[Python-Dev] Inconsistent string.replace() behavior (original) (raw)

Guido van Rossum guido@digicool.com
Wed, 09 May 2001 21:12:55 -0500

teststrop.py contains this line:

test('replace', 'one!two!three!', 'one@two@three@', '!', '@', 0) stringtests.py has this: test('replace', 'one!two!three!', 'one!two!three!', '!', '@', 0) IOW, the test suite insists that strop.replace('one!two!three!', '!', '@', 0) replace all matches but that string.replace('one!two!three!', '!', '@', 0) and 'one!two!three!'.replace('!', '@', 0) replace nothing. I've been thrashing like a madman trying to fix a common bug in both modules (in out-of-synch copies of mymemreplace), and every time I think I fix something "the other" module breaks. The above appears to be why. My opinion: the teststrop.py test is in error, and so was stropreplace() in stropmodule.c. I'm checking in changes accordingly, but won't mind getting yelled at if you disagree.

HMMMMMM! In Python 1.5, a count of zero always replaces all occurrences, both using string and using strop. In 2.0 and later, strop's replace(..., 0) still replaces all, but string's replaces none. The replace() method of strings and unicode objects agrees with string.py.

I think this change was made in the sake of ease of documenting the behavior: special-casing the count of zero is unexpected.

I very vaguely recall that it was discussed on this list.

So this suggests that test_string is correct, and string.replace() (and the methods) shouldn't be "fixed"!

But since we're not really supporting strop any more, I think that strop shouldn't be changed either. So we'll have to live with the difference -- sorry!

--Guido van Rossum (home page: http://www.python.org/~guido/)